Conventionally, in a cutting insert including a major cutting edge for cutting a workpiece and a second cutting edge, sometimes referred to as a flat cutting edge for smoothing the surface of the workpiece produced by the cutting, a minor cutting edge having a larger peripheral cutting edge angle than the major cutting edge is formed between the major cutting edge and the flat cutting edge from the viewpoint of damage reduction of a cutting edge. For example, Japanese Unexamined Patent Publication No. 2008-544872 discloses a cutting insert in which the angle formed between a major cutting edge and a flat cutting edge is 45°, and an intermediate cutting edge 11 (minor cutting edge) having a larger peripheral cutting edge angle than the major cutting edge is formed between the major cutting edge and the flat cutting edge.
However, in the cutting insert including the cutting edges having different peripheral cutting edge angles, such as the major cutting edge and the minor cutting edges, the chips generated from the individual cutting edges flow differently at a boundary of the major cutting edge and the minor cutting edge. Therefore, the chips might be twisted, and it might be difficult to perform chip treatment.